The format research objectives of this study involve the conception and formulation of new materials, or modifications of already existing materials, in order to improve the quality of crown and bridge prostheses both in porcelain-metal restorations as well as those made of complete cast pieces. In a broad concept this proposal involves: 1) Studying the nature of porcelain-metal (P/M) interface, identifying the type of compounds, if any, and their effect on P/M bond strength. In this phase, ion plating technic which is a relatively new technic will be used; 2) Studying wear of various alloy systems as well as the degree that they abrade other restorative materials. This will be accomplished by employing complete denture patients and utilizing specially designed dentures with detachable molar inserts. The inserts will be removed, mounted and digitized by means of a specially made stylis, to collect readings of the surfaces on the x, y, and z axes. A computer will receive these data and will plot the topology of surfaces. 3) Studying in-vivo and in-vitro the degree of tarnish of newly developed alloys and comparing the results to some those obtained from some commercially available alloys. In the in-vivo portion of the study, complete denture patients will be utilized and in each patient the degree of tarnish of 9 alloys will be determined; 4) Studying solidification patterns of cast alloys and flow patterns of molten alloy as influenced by various manipulative conditions. This study will be accomplished by modifying the arm of a casting machine; 5) Studying deformation of investments at casting temperature and how deformation is affected by the shrinkage force of cast alloys. This will be carried out by casting against reference rods made of high melting alloy. 6) Possible modification or alteration of the composition of dental investments to produce more accurate castings.